Field of the Disclosure
The disclosure relates to the field of display, more specifically, to the design of the AMOLED pixel circuit, and mainly provides a pixel circuit compensating the threshold voltage of the driving transistor.
Background
Traditional active matrix organic light-emitting diodes use 2T1C pixel driving mode, a switch transistor, a driving transistor and a storage capacitor to control the emitting of diodes. When the scanning signal is effective, the switch transistor is switched on to store the data signal in the storage capacity, the voltage signal stored by the storage capacity controls the conduction of the driving transistor, transforms the input data voltage signal into current signal, which the OLED need to emit to display different gray-scale. The main contradiction of the prior art is the threshold voltage of each driving transistor exists larger error with the process differences. With the low gray-scale images, using 2T1C structure may cause the difference between adjacent transistors reach to 20%. At the same time, when the size of the pixel power cord is longer, the power supply of the pixel circuit generates a larger IR drop, which causes serious uneven gray level. As a result, the pixel circuit actually applied eliminates the problems of short-range display and uneven length caused by the threshold voltage and IR Drop of transistors by the way of increasing circuits to compensate the threshold voltage and IR Drop. The design of the pixel circuit in prior art usually uses a compensating circuit in order to compensate the threshold voltage of driving thin-film transistor (TFT), such as in conventional 6T1C pixel circuit, mainly uses a single pixel circuit with compensation effect composed of six PMOS thin-film transistors and a storage capacitor, such a pixel compensating circuit often requires complex time sequence control, and the parameters of the electric current passing through the light-emitting diode have high correlation with the power supply voltage, so the compensation effect is poor.